By trigger I am assuming you meant trigger volume, so I will go with that.

(script startup scriptname
    <script commands here>
)

Most scripts will look similar to the example above, where "startup" refers to how you want the script to run (there are a few types: startup, continuous etc.), and "scriptname", of course, refers to the name of the script, which can be anything as long as you refer to them with this name properly in other scripts. And to answer your question, trigger volumes and flags can be named just about anything as long as you reference them in your script and they are big enough to detect the object you want them to detect.



Basically, create a trigger volume that detects if the player is in it, then spawns an AI encounter.
For example, if your AI encounter is called "bravo", you want the script to run continuously, your trigger volume is called "ai_spawner", and you want to call the script "spawn_aiz", you compile this script:

(script continuous spawn_aiz
   (if
		(volume_test_object "ai_spawner" (players))
		(ai_place bravo)
   )
)

Spawn the AI encounter, then get the specific squad of the AI encounter to enter a vehicle.
If your AI encounter is "sierra", the squad your driver is in is called "driver_squad" and it is part of the "sierra" encounter, your vehicle is a banshee with object name "this_random_shee" and its seat name is called "b-driver", you want the script to run on startup and you want to call your script "i_like_drivers", you compile this script:

(script startup i_like_drivers
    (ai_place (ai_actors sierra/driver_squad))
    (vehicle_load_magic this_random_shee "b-driver" (ai_actors sierra/driver_squad))
)

To sum it up, scripting is pretty much a mix and mashing of commands, you just need to find the right ones and place them logically in your script. If you need more script commands and flags, just download the Halo Scripting Bible (http://hce.halomaps.org/index.cfm?fid=2809) and play with the commands present there. If necessary, use the Halo Scripter tool (http://hce.halomaps.org/index.cfm?fid=2831) here to make your script.
Edited by sargejohnson on Aug 31, 2012 at 07:26 AM

EDIT: Ignore this, and next time have a single thread for your problems.
Edited by sargejohnson on Sep 1, 2012 at 12:12 AM

Set gametypes to "none" not "all games." That's for multiplayer maps only